If we're talking a theme for the game as a whole, you can never go wrong with the [url=https://www.youtube.com/watch?v=xEqSOst1dg8]classics[/url].

As for the X-Men? I have nooo idea. Been bouncing between a couple of different ones like [url=https://www.youtube.com/watch?v=dhqH4QpSgBI]this[/url], [url=https://www.youtube.com/watch?v=SBjQ9tuuTJQ]this[/url] or maybe [url=https://youtu.be/90WD_ats6eE]this one[/url]. Maybe even [url=https://www.youtube.com/watch?v=6lIqNjC1RKU]this one,[/url] though that's a little out there. Basically anything overtly political'll work for the team, though, since that's sorta their shtick- the X-Men without the politics are just a bunch of dorks in spandex.